1. Field of the Invention
The present invention relates to an image processing method and an image processing apparatus, which are capable of performing a compression coding and a decoding with respect to image data.
2. Description of the Related Art
A virtual microscope system includes a microscope apparatus capable of obtaining image data and a computer to process the image data. The virtual microscope system images the entire of a microscope slide on which a specimen is placed and store and display that image as a digital image. In the virtual microscope system, it is hoped that the virtual microscope system will have an operatibility equal to or higher than that of a real microscope.
One of operations hoped is, as in the real microscope, an operation of changing a focus position through rotating a slow-motion focus screw so as to allow an observation with respect to an arbitrary focus surface. The above-mentioned operation is an operation necessary for observing a sample having a certain thickness by using a microscope optical system having a very small depth of field. In particular, in the field of diagnostics, the above-mentioned operation is useful for grasping the form of a cell in three dimensions through observing while changing a focus by an examiner.
In the virtual microscope system, in order to realize the above-mentioned operation, data sets of images (hereinafter, referred to as “focus face images”) obtained by imaging a sample at a plurality of focus positions are necessary (see FIG. 1). Therefore, from one sample, a large amount of the image data is obtained. In view of this, in the virtual microscope system, a compression of the image data is performed.
For example, Japanese Patent Application Laid-open No. 2007-11977(hereinafter, referred to as Patent Literature 1) discloses a compression method including using an inter-frame encoding with respect to a plurality of focus face images. In the inter-frame encoding, a difference is determined between frames adjacent to each other. In addition, in Patent Literature 1, there is also described that a focus face to be the reference is defined, and a blur change depending on an optical parameter and a Z coordinate change from the reference focus face is utilized to perform a blur-compensation prediction, so that the compression is performed.
Further, another operation hoped to be realized in the virtual microscope system is a high speed switching of the magnification ratio of an image to be observed. In the real microscope, generally, the entire microscope slide is first viewed through a low magnification lens, and then a level of detail for the observation is gradually increased through switching the current lens to a higher magnification lens to be used one after another. In a typical virtual microscope system, various resolution image data sets obtained by gradually lowering the resolution from the original image data imaged are generated (see FIG. 2) and stored, and a pertinent image data is read and displayed according to an arbitrary resolution and an arbitrary specification of a display range of the image, which are determined by a user.